Because of the uncertainty in various geographical regions throughout the world as to the supply and cost of liquid hydrocarbon fuel, the dependence of these regions on such fuel as the sole fuel for internal combustion engines and the like, has adversely affected the economic stability and industrial development of such regions. On the other hand, certain of these regions have ready access to an inexpensive source of natural gas (CNG) and/or to a source of liquified petroleum gas (LPG) and thus, to utilize these sources to supplement the liquid hydrocarbon fuel would significantly improve the stability and development of these regions.
Various systems have heretofore been proposed, particularly with regard to diesel engines, in an effort to effectively supplement the fuel oil with a gaseous fuel. Such systems, however, have been beset with one or more of the following shortcomings: (a) the system is of a costly, bulky and complex construction; (b) the installation of the system requires substantial modification of the engine design; (c) the system is prone to malfunction; (d) the system is effective only within a narrow operating range of the engine; (e) the system requires an inordinate amount of service and maintenance; (f) the savings in fuel oil costs is only nominal; and (g) the system adversely affects the responses of the engine to various power demands.